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Perhaps we ought to explain "lead rust" in case someone is looking for a solution to that.
What it is -
first understand that all metals are crystalline. It shows most often on galvanized surfaces (zinc crystals) which grow there when the substrate (steel, say) is electroplated or dipped.
In a bulk solid, think of expanded polystyrene, or some wine corks. You only see the "beads" when you break it. When a metal like steel is cast, it's usually mechanically treated afterwards, which smears the crystals, called grains, at a (low) temperature where they stay smeared into each other.
Lead can reform its crystals at low temperatures, which is good because the strain comes out. If you dissolve the whitish oxide off old lead you can see a feint crazy-paving pattern sometimes - that's the grains.
So if you have a lead pipe which is draped over something like a cribbing/dwarf/support wall under a suspended floor, it starts off under slight tension on the upper side of the curve. If there's anything in the atmosphere which can corrode lead even slightly (often wee vapours under a bathroom, but sometimes just the ground), it attacks the grain boundaries. Think of a liquid running between the beads of exp poly..
The lead gets a tiny bit corroded , the grains separate a bit more because they aren't joined together any more, and eventually water can seep through the thickness of the pipe because it's porous.
Older "codes" of lead were thicker so lasted better. EG 1/2" can be code 7 or 8. The only solution is to replace the pipe. What you mustn't do is bend the pipe - it'll open the cracks more. (Such as you'd do if trying to get it into a coupler.)
As a botch, to cover it, you can scrape off the surface of the pipe and flow solder over it. You can of course wipe a load over it, but without moving it that's difficult. Getting it hot enough will be impossible if it's a mains pipe full of water, leaking through.
The other method , which can be effective, is to "work" the surface of the pipe. Start by putting tiny dents all over the area with a cross pein hammer, or the shaft of a screwdriver, etc.. Then with the right amount of pressure you can smudge the surface into itself,. With a bit of luck it'll hold while you sort out a proper repair.
If you break the pipe - which will be easy, it'll snap like a carrot, the corroded grains will show and they can be reddish. Hence "rust"!.
What it is -
first understand that all metals are crystalline. It shows most often on galvanized surfaces (zinc crystals) which grow there when the substrate (steel, say) is electroplated or dipped.
In a bulk solid, think of expanded polystyrene, or some wine corks. You only see the "beads" when you break it. When a metal like steel is cast, it's usually mechanically treated afterwards, which smears the crystals, called grains, at a (low) temperature where they stay smeared into each other.
Lead can reform its crystals at low temperatures, which is good because the strain comes out. If you dissolve the whitish oxide off old lead you can see a feint crazy-paving pattern sometimes - that's the grains.
So if you have a lead pipe which is draped over something like a cribbing/dwarf/support wall under a suspended floor, it starts off under slight tension on the upper side of the curve. If there's anything in the atmosphere which can corrode lead even slightly (often wee vapours under a bathroom, but sometimes just the ground), it attacks the grain boundaries. Think of a liquid running between the beads of exp poly..
The lead gets a tiny bit corroded , the grains separate a bit more because they aren't joined together any more, and eventually water can seep through the thickness of the pipe because it's porous.
Older "codes" of lead were thicker so lasted better. EG 1/2" can be code 7 or 8. The only solution is to replace the pipe. What you mustn't do is bend the pipe - it'll open the cracks more. (Such as you'd do if trying to get it into a coupler.)
As a botch, to cover it, you can scrape off the surface of the pipe and flow solder over it. You can of course wipe a load over it, but without moving it that's difficult. Getting it hot enough will be impossible if it's a mains pipe full of water, leaking through.
The other method , which can be effective, is to "work" the surface of the pipe. Start by putting tiny dents all over the area with a cross pein hammer, or the shaft of a screwdriver, etc.. Then with the right amount of pressure you can smudge the surface into itself,. With a bit of luck it'll hold while you sort out a proper repair.
If you break the pipe - which will be easy, it'll snap like a carrot, the corroded grains will show and they can be reddish. Hence "rust"!.
